I. Field of the Invention
This invention relates to a method for reducing the incidence of oral caries, more particularly, it relates to the application to oral surfaces of a sodium lauryl sulfate containing oral composition comprising a combination of antibacterial agents effective against streptococcus mutans and consequently reduce the incidence of caries.
II. Prior Art
It is known that dental caries are caused by the production of acid by certain specific bacteria. The particular bacteria generally recognized as the major etiological factor in dental caries is Streptococcus mutans (hereinafter S. mutans). S. mutans produce extacellular glucosyl and fructosal transferases enzymes from sugars which catalyze the formation of sticky, adhesive glucans and fructans from sucrose, which in turn promote the adhesion of bacteria to the oral surfaces. Further, S. mutans mutiple in the human environment and are a very high acid producer relative to other oral microorganisms.
Repeated cycles of such acid attack to tooth enamel initially results in microscopic demineralization or decalcification of the hydroxyapatite structure of the tooth enamel and the formation of an incipient carious lesion therein. While saliva provides a continuing source of calcium and phosphate to the tooth enamel which tends to remineralize the hydroxyapatite structure of the enamel, inhibiting and reversing the demineralizing carious process; once the acid attack has caused the demineralization to proceeded beyond an as yet not clearly defined state, the development of a full-fledged carious lesion and a clinically evident cavity occurs.
Dental plaque is a soft material formed of a complex mass of the bacteria that adherses to the very thin pellicle layer, formed primarily of salivary proteins, which surround each tooth. A 5-day-old plaque, if not disrupted as by brushing, can reach a thickness of about 60 m.mu.. A cariogenic plaque containing a high proportion of S. mutans, can often contain 2.times.10.sup.8 bacteria per mg wet weight and can rapidly ferment sucrose, glucose, or fructose to generate enough acid to lower the pH of the plaque to 5.5 or lower; whereupon demineralization of surface enamel occurs.
In the past, the main approach to reduction of caries has been the use of fluorides. The efficacy of fluorides in reducing caries is believed to be their direct inhibitory effect on enamel demineralization and promotion of the remineralization process. Indeed in U.S. Pat. No. 5,089,255, to Gaffar et al, remineralization is taught to be promoted by fluoride and xylitol. However, generally the maximum amount of fluoride ion approved by the U.S. Food and Drug Administration (FDA) for use in over-the-counter dentifrice formulations is limited to 1150 ppm.
An alternate or supplemental approach to fluorides is use of agents which effectively inhibit acid production by the bacteria within the plaque. This can be accomplished either by killing or removing the plaque and/or its constituent acidogenic bacteria or by inhibiting the bacterial metabolic processes, in particular the fermentation of carbohydrates and glucose to produce acid. Bactericidal compounds can, in theory, accomplish this, if they are suitably formulated and delivered, and have sufficient substantivity and efficacy.
S. mutans and dental plaque in general require the fermentation of substrates, not only as an energy source, but also for the production of structural and adhesion macromolecules like extracellular polysaccharides (glucans and fructans), lipoteichoic acid (LTA) and lectins. Xylitol, appears to cause a disturbance in the metabolism of fermentable carbohydrate by S. mutans and thereby decreases plaque formation and reduces plaque adhesion to the pellicle. Further, it is theorized that a toxic metabolite (xylitol-5-phosphate) is formed within the S. mutans cells, which may interfere with the glycolysis energy production and may also involve an energy-consuming futile cycle. These effects result in reduced caries, as has been documented by studies in humans employing high frequency use of xylitol in place of dietary sucrose, as well as, studies in candies and gums (e.g. Bar, Albert "Caries Prevention with Xylitol"; World Review of Nutrition and Dietetics, vol. 55:183, 1988).
Surface active agents or surfactants are required in dentifrice formulations to aid in the thorough dispersion of the dentifrice throughout the oral cavity when applied thereto, as well as, improve the dentifrice's cosmetic acceptability and the foaming properties. Sodium lauryl sulfate (hereinafter SLS) has supplanted virtually all other surfactants as the foaming agent in dentrifrices, whereby roughly 4 million pounds of SLS is used in oral products in the U.S. annually (Pader, Oral Hygiene Products and Practice, Marcel Dekker, Inc., N.Y., 1988). Previously, it had been concluded that the use of xylitol in toothpaste containing SLS would not have any antibacterial or caries reducing effect (Assev and Rolla, "SLS Containing Toothpaste Is Not A Suitable Vehicle For Xylitol", J. Dental Res., 75:316 (IADR Abstracts) 1996). This conclusion has been theorized to be due to SLS inhibiting the uptake of xylitol and inhibiting the formation of xylitol-5-phosphate (Jannesson et al., "Effect Of Xylitol In An Enzyme-Containing Dentifrice Without Sodium Lauryl Sulfate On Mutans Streptococci In Vivo", Acta Odontol Scand 55:212 (1997)).
U.S. Pat. No. 5,531,982 discloses an oral composition which inhibits plaque and reduces gingivitis and caries comprising a substantially water insoluble noncationic antimicrobial agent, such as triclosan, an acid reducing agent, such as xylitol and a water-insoluble siliceous polishing agent, further discloses the use therein of organic surface active agents, preferably anionic, nonionic or ampholytic in nature, examples of which include sodium lauryl sulfate. U.S. Pat. No. 5,531,982 by requiring a water-insoluble siliceous polishing agent is unduly limiting with respect to forumulation.
In companion co-pending U.S. patent application Ser. No. 08/160,337, filed Dec. 1, 1993, now U.S. Pat. No. 5,538,715, belonging to the same party-in-interest, an antibacterial antiplaque dentifrice was disclosed containing as an antibacterial agent, a substantially water-insoluble noncationic antibacterial agent such as triclosan, a antibacterial-enhancing agent and a solubilizing agent. U.S. Pat. No. 5,538,715 also disclosed the use therein of xylitol as an alternative sweetening agent. Such use of xylitol as a sweetener or a humectant in oral compositions which may or may not contain a noncationic antibacterial agent, such as triclosan, is known in the art.
There is a clear need in the art to for SLS containing oral compositions having anticaries efficacy as an alternative or supplement to the use of fluoride, that provide significant S. Mutans reduction and consequently reduce the incidence of caries formation and that are not unduly limited.